Connection mode
Zhejiang Zhengkang Industrial Co., Ltd.

Connection mode

Connection mode

Comparison of comprehensive performance of various thin-walled stainless steel water pipes
 
At present, the domestic thin-walled stainless steel connection mainly has single card pressure, double card pressure, ring pressure, socket welding and other ways. The following is a comprehensive comparison of these connections from the production process, performance, construction convenience, etc.
 

Connection mode
Performance

Single card pressure

Double card pressure

Ring pressure

socket welding

Technical sources

German M Company

German Viega Company

From the principle of clamping technology

Industrial Welding

Production standard

GB/T19228-2011

GB/T19228-2011

National Standard
GB/T33926-2017

Enterprise Standard

Application of technology

More than 60 years of foreign applications, domestic applications about 20 years

More than 50 years of foreign applications, domestic applications about 20 years

Domestic application for about 7 years

Domestic application for about 10 years

connection structure

The pipe fittings are crimped by special tools, and the section of the crimping interface is hexagonal (below DN50) or circular (above DN50), and the rigidity of stainless steel is used to connect. The wall thickness of the pipe fittings determines the rigidity. Therefore, the minimum wall thickness of the material required in the national standard shall not be lower than the national standard for clamping pressure.

Through special tools, crimp on both sides of the R port of the pipe fitting sealing ring. The cross section of the crimping interface is hexagonal (below DN50) or circular (above DN50). The rigidity of stainless steel is used for connection. The wall thickness of the pipe fitting meets the minimum wall thickness of the material required in the national standard.

The pipe fittings are crimped by special tools, and the section at the crimping interface is approximately bulged. The rigidity of stainless steel is used for connection. The wall thickness of the pipe fittings determines the strength of the rigidity. Therefore, the national standard stipulates that the ring pressure type has two different wall thickness standards for different requirements.

The outer edge of the pipe is welded by the argon arc welding gun, and the pipe fittings are connected by the molten stainless steel liquid.

Connection structure characteristics

The R port of the pipe fitting is completed in the factory, and the stress concentration is eliminated through the solid solution process.
The cross section of the interface is hexagonal, which will not rotate due to the installation of pipe accessories (threaded connection is mostly used below DN50).

The hexagonal deformation of the pipe fittings is smaller than that of the bulging circle of the ring pressure, the stress concentration phenomenon is weaker than that of the ring pressure, the stress is controlled in an appropriate range, and the joint will not be damaged by stress concentration.

The basic characteristics are the same as single card pressure

 

Because there is a socket section outside the R port, the anti-pulling force is effectively improved, the damage to the shape of the R port due to external force is effectively protected, and the compression ratio of the protective seal ring is improved.
Effectively protect the sealing ring from dust and ultraviolet damage.

The pipe fitting has no R port, and special tools shall be used for crimping to form R port during installation. Stress accumulation exists at R port, and solution heat treatment cannot be carried out on site to relieve stress. The joint section is approximately circular, which may cause leakage risk due to the rotation of pipe fittings caused by the installation of pipe accessories.

The pipe is thin, the welding process is easy to weld through the pipe, once welded through, not easy to repair.
High temperature during welding causes damage to the internal metallographic structure of stainless steel, resulting in low corrosion resistance at the weld.
Can not complete the solid solution after welding, pickling passivation process, so that the weld is in the weakest state
 

sealing structure

O-ring, linear longitudinal seal, sealing each point compression ratio is uniform, in all the seal ring shape, O-type elasticity is the best

O-ring, linear longitudinal seal, sealing each point compression ratio is uniform, in all the seal ring shape, O-type elasticity is the best

Annular compression wide band cavity seal, rectangular section belongs to surface seal, because 100% ring compression cannot be guaranteed, the compression ratio of each point on the sealing circumference is uneven, and there is a risk of leakage.
The structure of rectangular cross section is more suitable for flange connection

No sealing ring

Sealing material

Butyl chloride, permanent compression is relatively high, in line with national standards.

Seal ring is black, more resistant to ultraviolet aging

EPDM rubber, in line with national standards, permanent compression is relatively good, aging resistance, is currently widely used in high health requirements, high sealing requirements of various water supply accessories materials. The life of civil water supply pipeline is verified by Shanghai Polymer Research Institute to be higher than that of pipeline.

Seal ring is black, more resistant to ultraviolet aging

EPDM rubber, in line with national standards, permanent compression is relatively good, aging resistance, is currently widely used in high health requirements, high sealing requirements of various water supply accessories materials. The life of civil water supply pipeline is verified by Shanghai Polymer Research Institute to be higher than that of pipeline.

Seal ring is black, more resistant to ultraviolet aging

No sealing ring

Pipe fitting process

Complex production process and high technical content
Threaded fittings using silica sol precision casting, pipe fittings using cold stamping, and after solid solution, pickling passivation treatment

The sealing ring has been assembled in the R port of the pipe fitting

Same as single card pressure

Simple production process
Pipe fittings and threaded parts are produced by extrusion
The pipe fitting has no R port for the sealing ring.
 

cold stamping process

Other accessories (e. g. threaded interface)

Silica sol precision casting, can ensure the physical properties of the casting, no stress concentration phenomenon.

Threaded fittings hex size specifications in line with national standards, available standard wrench construction, convenient construction

Silica sol precision casting, can ensure the physical properties of the casting, no stress concentration phenomenon.
Threaded fittings hex size specifications in line with national standards, available standard wrench construction, convenient construction

Seamless stainless steel pipe cold extrusion production, easy to form stress concentration phenomenon
The external hexagon size of threaded fittings is not standardized, and standard wrenches and pipe tongs cannot be used.

Seamless stainless steel pipe cold extrusion production, easy to form stress concentration phenomenon
The size and specification of the outer hexagon of the threaded fittings are not standardized, and wrenches cannot be used, only pipe tongs can be used, which is inconvenient for construction.

Working pressure

Working pressure of 1.6MPa, in line with national standards

Working pressure of 1.6MPa, in line with national standards

Working pressure of 1.6MPa, in line with national standards

Working pressure of 1.6MPa, in line with national standards

Pipe Specification

In line with the national standard GB/T19228, take DN25 as an example, the actual inner diameter of the tube is 26.58mm.

Same as single card pressure

In line with the requirements of the national standard GB/T33926, take DN25 pipe as an example, the actual inner diameter is 23.8mm

DN25 pipe as an example, the actual inner diameter is 23.8mm

Pipe wall thickness

Comply with national standard

Comply with national standard

According to different needs, there are two wall thicknesses lower than and equal to the national standard of card pressure.

Below the compression standard

Material cost

Due to the wall thickness of the pipe, the total cost of the pipe and pipe fittings is reasonable.

The cost of pipes and fittings is reasonable.

Because the outer diameter and wall thickness are lower than the national standard requirements and the molding process steps are less than the pressure, the total cost is low.

Because the outer diameter and wall thickness of pipes and fittings are lower than the national standard requirements, the weight of a single product is 70-80% of the total cost of the pressed product.

construction cost

One-time crimping molding, short installation time

The process is simple, just insert the pipe directly into the pipe fitting, because the pipe fitting has been installed with a sealing ring. Save installation time

Same as single card pressure

The installation time is long, and it takes two or three times to complete the crimping, resulting in longer working hours.
The process is complicated, and the sealing ring should be installed on the pipe before crimping. If the seal ring is not installed in place, pull out the tube and reinstall it. This in turn causes installation to take nearly 15% more time than clamping.

Argon arc welding wages higher than ordinary water wages

Need welding wire, argon and other accessories, accessories, power electricity, these accessories account for about 9% of the material.
The installation time is long, about 1.6 times the installation time of the card
The preparation time of internal argon protection is basically the same as that of clamping and crimping.
 

Service life

Stainless steel for 70 years, because the wall thickness conforms to the national standard, it has a strong ability to resist the corrosion of other environmental factors.
Sealing ring, chlorinated butyl rubber up to 50 years

Same as single card pressure
Sealing ring, using EPDM rubber, the service life is higher than the pipeline life

Stainless steel for 70 years, if you choose a small wall thickness series, the corrosion allowance is lower than the clamping pressure, and there is a danger of corrosion by other environmental factors.

Stainless steel is 70 years old, but the wall thickness is thinner than the clamping type, the corrosion allowance is lower than the clamping pressure, and there is a danger of corrosion by other environmental factors.

If the welding process is not in place at the weld seam, quality problems have occurred.

Fire requirements

No open flame, no fire hazard

No open flame, no fire hazard

No open flame, no fire hazard

There is fire hazard during installation.

Conveying energy consumption

energy saving

energy saving

The inner diameter is small, like transporting the same amount of water in the same time, and the energy consumption is high.

The inner diameter is small, like transporting the same amount of water in the same time, and the energy consumption is high.

There is residual welding slag on the inner wall of the pipe, and the water flow resistance is large, which increases energy consumption.

Routine maintenance

Maintenance-free

Maintenance-free

Maintenance-free

If the welding process is not in place, the maintenance cycle is short.

 

Analysis:
1, single from the material procurement cost comparison, socket welding cost is the lowest, followed by ring pressure.
2. From the comparison of product safety, double card pressure is better than single card pressure, single card pressure is better than ring pressure and socket welding.
3, from the installation cost analysis, double card pressure, single card pressure is the lowest, ring pressure and welding is higher.
4, from the analysis of fire requirements, socket welding risk is high, especially with the interior decoration at the same time construction, easy to cause fire.
5. From the perspective of sealing performance, clamping pressure and socket welding are better than ring pressure.
6, from the daily maintenance and energy consumption analysis, card pressure and socket welding is better than ring pressure.
Summary:
Stainless steel material cost and installation cost of the comprehensive cost, these four connection methods are similar, but if you consider the service life, maintenance costs and daily energy consumption, double card pressure and single card pressure is optimal. The material procurement cost of ring pressure and socket welding is lower. From a dialectical point of view, things are both opposites and unity. Reducing the amount of product materials can reduce material costs, but installation costs and daily maintenance costs will increase accordingly, and the service life will be reduced accordingly. Although the amount of raw materials for double-card pressure and single-card pressure products is slightly higher than that of ring pressure and socket welding, it greatly improves the life of the product, reduces the daily maintenance cost and reduces the energy consumption. Therefore, the connection mode of double card pressure and single card pressure is a better thin-walled stainless steel connection mode.